Files in this Data Supplement:

• Methods, Legends, and Table - (Microsoft Word) (356 kb)
• Movie I - (AVI) (249 kb). The activation sequence of the SAN. The movie is an animation of the activation sequence in Fig. 1A. Two overlapping fields of view are shown. The CT, the main branch of the CT and the pectinate muscles are in the bottom left field of view. The intercaval region is in the top right field of view. The action potential is first initiated in the intercaval region. It propagates rapidly from here to the CT and then into the right atrial free wall. Conduction in the opposite direction (towards the interatrial septum) is slow. This corresponds to the conduction block zone.
• Movie II - (AVI) (3.55 MB). The 3D model of the SAN. The movie is an animation of the model shown in Fig. 6. The movie begins with the surface of the preparation (yellow). The blue line shows the position of the sinoatrial ring bundle. The surface is next stripped away to reveal the underlying myocytes. Atrial muscle is shown in pink, the periphery of the SAN is shown in blue and the centre of the SAN is shown in red. The atrial muscle is then stripped away and this reveals the pulsating sinus node artery. Finally the SAN periphery is stripped away to leave just the SAN centre.
• Movie III - (AVI) (3.58 MB). The 3D model of the SAN within a simplified right atrium. The movie is an animation of the model shown in Fig. 8C. To show the SAN in situ, the SAN model has been morphed onto a simple framework model of the right atrium. For further explanation of the movie, see the legend to Data Supplement Movie II.
• Data Supplement File I - (zipped TXT file) (5.29 MB; expands to 40 MB). The 3D model of the SAN. The mathematical array is given as a compressed text file. Each line gives the X, Y and Z coordinates (in mm) of a point and the cell type (1, connective tissue; 2, atrial cells; 3, peripheral SAN tissue; 4, central SAN cells; 5, sinus node artery) at the point.
• Figure I - (JPEG) (293 kb). Immunofluorescence labelling of NF-M and ANP in isolated SAN cells. A-F, immunofluorescence labelling of NF-M (left) and ANP (right) in rod-shaped atrial cells (A, B), elongated spindle-shaped SAN cells likely to be from the periphery of the SAN (C, D) and spider-shaped SAN cells likely to be from the centre of the SAN (E, F). There is cytoplasmic labelling of NF-M in the SAN cells and granular cytoplasmic labelling of ANP in the atrial cell (corresponding to ANP-containing vesicles).
• Figure II - (JPEG) (578 kb). SAN cells wrapped around bundles of atrial cells in the periphery of the SAN. A-C, three consecutive tissue sections stained with Masson’s trichrome (A) and labelled for NF-M (B) and Cx43 (C) using immunoenzyme. In A, myocytes are stained purple and connective tissue is stained blue. In B and C, positive labelling is shown by the dark brown colour (punctate in the case of Cx43). The sections are from the intercaval region towards the superior part of the SAN as shown in Data Supplement Fig. IV. SAN cells (NF-M-positive/Cx43-negative) can be seen to surround bundles of atrial cells (NF-M-negative/Cx43-positive), particularly on the left. An example is highlighted by arrow 1. On the right, note that there is a thick layer of atrial cells (arrow 2) lying below a layer of SAN cells just a few cells thick (arrow 3). D, E, high magnification views of the boxed regions in B and C. Note the NF-M-positive/Cx43-positive nodal cells outlined by the red dashed line.
• Figure IIIA - (JPEG) (438 kb). The 61 Masson’s trichrome stained sections used to construct the model. Distance in mm from top of preparation shown. For the 3D model of the SAN, these sections provided the outline of the tissue and the division into myocytes (stained purple), connective tissue (stained blue) and adipocytes (appear white). The difference in background colour between the two panels is not significant.
• Figure IIIB - (JPEG) (530 kb). See Figure IIIA legend.
• Figure IV - (zipped TIF) (10.1 MB; expands to 39.0 MB). Location of tissue shown in other figures. A, Masson’s trichrome stained sections showing the location of the tissue (boxed areas) shown in Data Supplement Fig. II and Figs. 3-5. The tissue sections correspond to the appropriate green lines shown in B. B, endocardial view of the myocytes of the 3D model of the SAN. The green lines show the approximate positions of sections shown in Data Supplement Fig. II and Figs. 3-5. The yellow dot marks the position of the leading pacemaker site. The sinoatrial ring bundle is shown in blue.